1. Field of the Invention
The present invention relates to a direction turning passage of a rolling bearing for an infinite rectilinear motion and, more particularly, to a direction turning passage in which the movement of rolling members from the track groove to the direction turning passage is made smooth and thereby enabling the slide resistance of the bearing to be reduced.
2. Description of the Prior Art
Hitherto, in slide members, rolling members which have passed through the track serving as a load range of the rolling members are led to an arc-like direction turning passage consisting of a uniform radius and are moved to a return passage set in parallel with the track.
It is obvious from the Official Gazette of Japanese Patent Application No. 245933/1983 filed previously by the same applicant as this invention that the movement of the rolling members in the infinite circulating passage becomes smooth as the radius of the arc of the direction turning passage is increased.
However, in case of actually designing bearings, there is a limitation of a size of the bearing and as the radius of the arc of the direction turning passage increases, the width of the bearing and the length in the direction of the axis are also enlarged, so that the radius of the arc is unconditionally limited and determined. Consequently, this also results in a limitation of the reduction of the slide resistance between the direction turning passage and the track.
Recently, a number of bearings for a rectilinear motion have been used in the industries relative to the mechanical/electronical fields and at the same time, smaller-sized bearings for a rectilinear motion having smaller slide resistances are demanded. In such a situation, it is a large subject to reduce the slide resistance.
In general, the rolling members which enter the direction turning passage from the straight track strike the outside wall surface of the direction turning passage and the moving direction is changed. Thus, as the rake angle adapted to guide the rolling members becomes small, the resistance at this time is reduced. In other words, the resistance becomes small with an increase in the radius of the outer periphery of the direction turning passage. However, on the contrary, a problem such that the width and length of the bearing become large is caused.